Saturday, September 24, 2011

Why 'good' sugar is the secret to a slim figure (?)

The popular article below is a fanciful elaboration of the academic original. I therefore append the academic original. The earth shattering finding of the academic original was that when you are low on nutrients you feel hungry -- and that the brain has got something to do with that

Eating fresh fruit and vegetables helps people resist the temptation of waist-expanding treats, scientists have found.

When our supplies of glucose - found in carbohydrates - drop we begin to lose our ability to control desire, while our urge to eat increases. The lack of glucose – which is used to power the brain – makes us helpless against the urge to reach for high-calorie foods, researchers said.

Obese people are particularly vulnerable, with even the slightest drop in glucose prompting irresistible cravings for carbohydrates, from which we get most of our sugar.

These can be "good" carbs, such as fresh fruit and vegetables, brown rice and pasta and wholemeal bread, or "bad" varieties which include white bread and sugar, fizzy drinks, cakes, crisps and other packet snacks.

Making sure the brain's glucose levels do not drop could be the secret to staying slim, a study published in the Journal of Clinical Investigation suggested.

Eating less and often could lower the chance of succumbing to the temptation of high-calorie foods, particularly for obese people, the researchers said.

Prof Rajita Sinha, of Yale University in America, said: "The key seems to be eating healthy foods that maintain glucose levels.

Volunteers were given injections of glucose and their brains were scanned while they were shown pictures of high and low calorie foods, as well as other objects.

When glucose levels were lower, two areas of the brain which regulate pleasure prompted the desire to eat while the prefrontal cortex – which gives us self-control – lost its ability to control the impulses.

Circulating glucose levels modulate neural control of desire for high-calorie foods in humans

By Kathleen A. Page et al.


Obesity is a worldwide epidemic resulting in part from the ubiquity of high-calorie foods and food images. Whether obese and nonobese individuals regulate their desire to consume high-calorie foods differently is not clear. We set out to investigate the hypothesis that circulating levels of glucose, the primary fuel source for the brain, influence brain regions that regulate the motivation to consume high-calorie foods. Using functional MRI (fMRI) combined with a stepped hyperinsulinemic euglycemic-hypoglycemic clamp and behavioral measures of interest in food, we have shown here that mild hypoglycemia preferentially activates limbic-striatal brain regions in response to food cues to produce a greater desire for high-calorie foods. In contrast, euglycemia preferentially activated the medial prefrontal cortex and resulted in less interest in food stimuli. Indeed, higher circulating glucose levels predicted greater medial prefrontal cortex activation, and this response was absent in obese subjects. These findings demonstrate that circulating glucose modulates neural stimulatory and inhibitory control over food motivation and suggest that this glucose-linked restraining influence is lost in obesity. Strategies that temper postprandial reductions in glucose levels might reduce the risk of overeating, particularly in environments inundated with visual cues of high-calorie foods.

J Clin Invest. doi:10.1172/JCI57873. 2011

Diet police mug the very hungry caterpillar

ONE Sunday morning the warm sun came up and -- pop! -- out of the egg came a tiny and very hungry caterpillar. He started to look for some food. He ate through an apple, two pears, three plums, four strawberries and five oranges.

Readers of the classic children's book know what happens next. Still hungry, the caterpillar gorges on one piece of chocolate cake, one ice cream cone, one pickle, one slice of Swiss cheese, one slice of salami, one lollipop, one piece of cherry pie, one sausage, one cupcake and one slice of watermelon.

But it seems the grub of today has different -- and healthier -- tastes. In a rendition of the Eric Carle tale performed by Flemington Primary School prep students in Melbourne, the caterpillar spends his Saturday munching through a bowl of cereal, a cheese-and-tomato sandwich on brown bread, a glass of low-fat milk, a slice of (unspecified) cheese, a bowl of spaghetti, steamed broccoli, a piece of chicken, a piece of fish and a tub of low-fat yoghurt.

Curiously, he still ends up with a stomach-ache.

But instead of cleansing his system with a nice green leaf, as Carle wrote, he washes it away with a big bowl of vegetable soup. "After that he felt much better," the kids recited.

All this good living duly produces a glorious butterfly. But that is not where the revised story ends. Once he gets his wings, the butterfly signs up for "PMP", which stands for the Perceptual Motor Program, a fancy prep way of saying exercise class.

Carle might wonder about the reinvention of his most famous book, which has been translated into 55 languages and has sold 33 million copies since it was first published in 1969.

The author of The Very Hungry Caterpillar is now 82, divides his time between the Florida Keys and the hills of North Carolina, and is a regular blogger. The Weekend Australian emailed him to ask his thoughts on the "improvements" made by Flemington prep, but he has not yet replied.

No doubt he would have had a chuckle to observe the kids' accompanying artwork. Mostly, they were pictures of lollipops.


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